This invention refers to a rolling piston rotary compressor and, more particularly, to a discharge system for such compressor type which is usually used for small refrigerating systems.
Generally, rolling piston rotary compressors have direct suction and discharge into the housing, that is, they work under a high pressure within the housing. As a result, the gas which is within the housing becomes an excellent means to carry noise. Thus, the pulses in the discharge of compressed gas within the compressor assembly into the housing are carried by the gaseous means itself (the inner atmosphere in the housing under high pressure) reaching the housing walls which vibrate and thereby cause noise. Therefore, in this type of compressor it is very important to provide a good insulation against the pulses from the discharge gas and consequently against any noise thereby generated.
Another technical problem is one that, due to the arrangement of the parts in the assembly of a rolling piston rotary compressor, the walls of the housing covers, where the discharge port is usually placed, have to be thick (from 7 to 10 mm) to bear the high pressures produced within the compressor assembly. This causes the discharge port neck to be too long (from 3 to 5 mm) even when a recess in the outlet valve seat is used. This excessive extension increases the discharge flow pressure loss, thereby resulting in increasing the compressor energy consumption. Therefore, to reduce such energy loss, the discharge port neck in the compressor assembly has to be as short as possible.
U.S. Pat. No. 4,573,879 shows the discharge dampening system most commonly used in rolling piston rotary compressors. Basically, such known system has a muffler chamber with several volumes made of a stamped plate. Although it is a very simple solution, the disadvantage is that the plate which makes up the muffler chamber thickness is very small, thereby producing an incomplete dampening of the discharge flow noise, since the muffler chamber walls themselves vibrate thereby exciting pulses in the inner housing atmosphere that, in turn, carries such vibrations outside the compressor in noise form. A way which is usually used to increase the rigidity of the dampening chamber is shown in the drawing for the U.S. Pat. No. 4,636,154. In this arrangement, the muffler chamber volumes are formed on the compressor secondary bearing itself and covered by an outer cover in the form of a thick plate.
Some drawbacks to these approaches are that the manufacturing of the secondary bearing is complex, making it incompatible with the common machining processes. Therefore, the process of obtaining the secondary, bearing by metal powder sintering is usually employed. Also, in this process, the drawbacks inherent to the design complexity and the several compaction heights of the sinterized metal powder makes this part very expensive.
Another disadvantage of this solution is that the compressor assembly mounting screws have to be very long in size, which will probably cause some other problems concerning vibration and lack of rigidity in the compressor assembly.
It is also worthwhile saying that both of the prior art arrangements discussed above have a discharge port neck with a relatively long size, thus causing some pressure losses as already mentioned.